1. Field of the Invention
This invention relates in general to video signal de-interlacing and interpolation. More particularly, the invention relates to a method and apparatus for properly interpolating and spatially positioning video lines from an arbitrarily sized video field to create an arbitrarily resized progressive scan frame.
2. Description of the Prior Art
Current state-of-the-art de-interlacing involves converting an interlaced scanned video signal into a progressive scan (sometimes referred to as sequentially scanned) video signal with exactly double or quadruple the number of output lines. The output size restriction makes it very difficult and expensive to de-interlace video fields for use in an application that requires an arbitrarily sized output progressive scan video window. The original video signal is composed of interlaced scanned odd and even fields. These fields are mapped into progressive scan frames through a process of spatial interpolation and positioning that produces exactly double or quadruple the number of input lines per field.
De-interlacing has many applications including slow motion playback, computer video-in-a-window displays and large screen projection television systems to name but a few. All of these applications require the high quality and performance provided by the generation of progressive scan frames using a de-interlacing process.
Producing high quality de-interlaced video signals is difficult. An object in one video field may be in a different spatial position in the next field which makes it very difficult to properly combined the fields into a single progressive scan frame. In such an application, advanced and expensive methods of temporal and vertical interpolation are required to give satisfactory results. One common prior art method of interpolation uses motion detector circuitry to identify areas of a video field which change over time. These changing areas are interpolated differently from static regions to ensure a high quality image.
The complexity and expense of motion detector circuitry and advanced interpolation circuitry restricts the flexibility and affordability of such prior art de-interlacing systems. These systems have been highly optimized to produce either double or quadruple the number of input lines per field, as discussed above.
Examples of well known prior art de-interlacing systems are described in the following publications and patents:
Publications
Watkinson, John, "The Art of DIGITAL VIDEO--2nd Edition", Focal Press 1994, pp. 180-185.
U.S. Patent Documents
U.S. Pat. No. 5,291,280 March 1994 Faroudja; Yves C.
U.S. Pat. No. 5,070,403 December 1994 Wilkinson, Basingstoke